An air conditioner is an apparatus that cools or heats indoor space by using a refrigeration cycle. The refrigeration cycle includes a compressor, a condenser, an expansion device and an evaporator that are sequentially connected to each other by pipes. A refrigerant circulates the compressor, the condenser, the expansion device, and the evaporator through the pipes.
A flow path is formed in the condenser and the evaporator in the refrigeration cycle. The refrigerant is heat-exchanged with surroundings while passing through the flow path formed in the condenser and the evaporator to be condensed or evaporated, and the condenser and the evaporator serve as a heat exchanger. The flow path is used to allow the refrigerant to flow therethrough, and the refrigerant flows in the flow path. Hence, the flow path is a concept that is included in the meaning of the term the pipe in a broad sense.
Pipes connect the components of the refrigeration cycle to each other, and are used as a flow path of the compressor and the condenser. Conventional pipes are typically made of a copper (Cu) material. However, pipes made of copper may have a few problems.
First, copper has a limitation in reliability due to corrosion. For example, in the case of a chiller heat transfer pipe, the chiller heat transfer pipe is cleaned or replaced to remove scales, etc. therein.
Next, copper does not have a sufficiently high pressure resistance property when it is used for a flow path of a new high-pressure refrigerant such as R32. If a pipe made of copper is used as a flow path of a new high-pressure refrigerant, the pipe may not endure high pressure and may thus be damaged as time elapses.
In order to address such problems of copper pipes, Korean Patent Laid-Open Publication No. 2003-0074232 discloses a stainless steel pipe, which is made of a stainless steel material. In general, stainless steel has a strong corrosion resistance and a sufficiently high pressure resistance property as compared with copper. Thus, tubes or pipes made of stainless steel can address the problems of copper pipes, such as corrosion and damages at high pressure.
However, a conventional stainless steel material including the stainless steel pipe disclosed in Korean Patent Laid-Open Publication No. 2003-0074232 has properties of excessively high strength and hardness as compared with a copper material, and thus, may have a problem of processability, which may not be present in copper pipes.
Pipes used in an air conditioner are typically formed not only in a linear shape but also in a curved shape due to spatial constraints. In other words, one portion of the pipe may be formed in a linear shape, and another portion of the pipe may be formed in a curved shape. A linear pipe refers to a pipe extending in one direction along a straight line, and a curved pipe refers to a pipe curved along a curve.
However, since the conventional stainless steel material has properties of excessively high strength and hardness, it may be difficult to manufacture a pipe having a curved shape. For example, a linear pipe made of a stainless steel material is processed to have a curved pipe by applying a mechanical force to the linear pipe. However, as shown in FIG. 1, since the linear pipe is not completely plastically deformed but partially plastically deformed, and sufficient processing may not be performed to obtain a desired curved pipe.
Stainless steel has typically properties of high strength and high hardness, and thus, it may be difficult to improve the processability of a stainless steel material. Moreover, since pipes typically occupy 10% or more of the total material cost of an air conditioner, the demand for improving the performance of the pipes and reducing the cost of the pipes is continuously increasing.